A high-voltage integrated circuit, in which one or more high-voltage transistors are disposed on the same chip together with low-voltage circuits, is widely used in a power control system, for example, such as a switching power supply or a motor driver. A high-voltage integrated circuit includes a high-voltage unit and a low-voltage unit. Level shift elements are arranged between the high-voltage unit and the low-voltage unit to level-shift a signal from the low-voltage unit and provide the level-shifted signal to the high-voltage unit. Laterally diffused MOS (LDMOS) transistors are used as the level shift elements. However, the LDMOS transistors have limitations with respect to a low breakdown voltage and a high on-resistance. In addition, when bootstrap diodes are connected to the outside of the high-voltage integrated circuit, the entire module size may increase, and thus its integration may be difficult.